Cleaning solution concentrate and method of preparing same



United States Patent 3,481 877 CLEANING SOLUTION 'CONCENTRATE AND METHOD OF PREPARING SAME Karl Moll, Hatboro, Pa., assignor to Amchem Products, Inc., Ambler, Pa., a corporation of Delaware N0 Drawing. Filed Feb. 27, 1967, Ser. No. 619,034 Int. Cl. C23g 1/22; C23f 1/00 US. Cl. 252-795 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the art of cleaning and/or etching aluminum surfaces. More particularly the invention provides a concentrated aqueous chemical composition for use in cleaning and/or etching aluminum surfaces prior to subsequent treatment, which can be used for both initial preparation of the treating solution and replenishment thereof. In addition, the invention, when used as hereinafter prescribed, will not only be most effective in cleaning the above mentioned aluminum articles but will also, when compared to other aqueous alkaline cleaning materials, yield a treating solution which provides for a minimum amount of equipment maintenance to the user.

In accordance with another aspect of the invention, a method is provided for compounding a superior aqueous concentrate for use in cleaning and/ or etching aluminum, which method insures production of a stable concentrate.

By way of background, it should be pointed out that the use of aqueous alkaline cleaning solutions for treatment of aluminum surfaces is a well established commercial practice. For example, it is known from US. Patent Nos. 2,869,267 and 2,939,826 that the use of solutions containing an alkaline metal hydroxide and a tertiary amino-alcohol will provide satisfactory cleaning and/or etching of metal surfaces, particularly aluminum surfaces.

It is also known from US. Patent Nos. 2,615,846 and 2,584,017 that the incorporation of an alkali metal gluconate into an alkaline cleaning or etching solution serves effectively to prevent or to retard hard to remove scale formation in such cleaning and/or etching operations.

In many instances where aluminum articles are being cleaned and/ or etched, it has been found that undesirable precipitates form in the etching solutions; thereby seriously complicating use of the solutions and creating equipment maintenance difiiculties. Such precipitates tend to interfere with the cleanliness of the aluminum surface and subsequent processing treatments thereby adversely affecting the surfaces appearance. Various attempts have been made to overcome this problem through the use of different additives in the aqueous treating solutions. Among such attempts has been the inclusion of gluconates or tartrates into alkaline solutions, including such solu tions which also contain tertiary amino-alcohols and s01- vents, and such solutions have been somewhat successful.

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However it has heretofore not been possible to formulate a concentrated composition of all of the essential ingredients required in the treating solution.

For this reason it has been necessary, in preparing aqueous etching or cleaning solutions, to utilize several separate make-up chemical formulations in order to achieve the desired treating bath.

With the foregoing in mind, the principal object of the present invention is the provision of a stable, consolute, concentrated, aqueous chemical composition, which provides, upon simple dilution with water, all of the essential components required for purposes of cleaning and/ or eaching aluminum, so as to produce thereon clean, bright surfaces suitable for further processing in the metal treating industry.

Another object of the present invention is the provision of a method for compounding a stable consolute cleaning concentrate.

The present invention is based upon the surprising discovery that a concentrated aqueous solution containing, per parts of solution, by weight,

(a) about 4.6 to about 42 parts of sodium and/ or potassium hydroxide,

(b) about 0.15 to about 30 parts of gluconate ion,

(0) about 1.7 to about 38 parts of an ethanolamine compound,

(d) about 0.43 to about 54 parts of an ethylene-glycol compound, and

(e) about 19 to about 64 parts of water,

which solution is stable and consolute as hereinafter defined, will provide, upon dilution with water to the desired use strength, an aqueous solution for cleaning and etching aluminum surfaces.

The cleaning concentrates of the present solution are used for cleaning and/ or etching aluminum in dilute form. Generally, they are diluted with water for use, sufiicient Water being employed to yield a final concentration, for example, from 1 gram to 15 grams per liter of potassium hydroxide or equivalent.

It should be noted that not all concentrated aqueous solutions containing the above listed components within the ranges set out form the stable consolute solutions which the within the purview of this invention. The components must further be formulated within the above ranges, as hereinafter explained, to produce solutions which are both stable and consolute, this being accomplished by use of appropriate amounts of the active ingredients within the above ranges. By the term consolute, as utilized in this specification and claims, is meant that these solutions must possess the property of complete homogeneity to the total absence of phase separation. A two-phase concentrate forms an undesirable starting material for aluminum cleaning solutions because of the considerable practical difiiculties in metering an appropriate amount of such a two-phase solution into a cleaning bath. By the term stable, as used herein, is meant that the consolute solutions of this invention will retain their homogeneity within the temperature range of 65l20 F. when slowly heated to this temperature range. A cleaning concentrate which is not stable in the sense that the term is used herein is undesirable because it will tend to separate into an objectionable two-phase solution under ordinary storage and transport conditions.

So far as concerns the amounts of each respective component in the concentrated, stable, consolute solutions of this invention, it has been found that the relationships of the components to each other is critical and must be maintained in accordance with prescribed guidelines as described below.

Where the amount of gluconate ion employed is below about 0.15% by weight of the total formulation, the combined desired chelation effects and brightening of treated aluminum surfaces will not be obtained and hard, scaly deposits will be formed in the aluminum treating tanks. Conversely, increasing the amount of gluconate above about 30% by weight of the total formulation, may adversely effect formulation stability causing a separation of phases.

The gluconate ion may be added to the formulation as gluconic acid or the sodium or potassium salts thereof. If desired this acid or its salts may be dissolved in a portion of the water and added to the formulation as an aqueous solution.

The water component must be present in an amount of from about 19% to about 64% by weight, based on the weight of the total composition. Where formulations are prepared containing less than about 19% by weight of water, the improved stability otherwise obtainable with this invention will not always be realized. Conversely, if more than about 64% by weight of water is employed, the formulations will not provide a sufiicient concentration of active aluminum cleaning and etching components so as to represent a commercially feasible concentrate.

The use of an ethyleneglycol compound has been found to be essential to the formulations of this invention in order to provide an adequate level of soil removal from the aluminum articles being treated.

The types of ethyleneglycol compounds which have been found to be suitable for use in the concentrated formulations of this invention include ethyleneglycol and derivatives thereof and have the formula:

wherein R is selected from the group consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, and R is selected from the group consisting of hydrogen, the -CH CH OH radical and the radical. As used herein, ethyleneglycol compound includes ethyleneglycol and derivatives thereof as defined by the above formula.

A prime advantage in the utilization of these materials, in comparison to other organic solvents, is their water solubility and tolerance toward inorganic ions in solution, which eliminates the necessity of adding solubilizing and/or emulsifying agents to the formulations in order to prevent solvent separation upon dilution to use concentration.

Regarding the amount of ethyleneglycol compound present in the formulations of this invention, it has been found that if less than about 0.43% by weight of the total formulation of ethyleneglycol compound is used the desired cleaning action of aluminum surfaces may not be realized. Conversely, if more than about 54% by weight of this constituent is employed, the resulting concentrated formulations will lack stability in accordance with the teachings of this invention.

With respect to the ethanolamine compounds, these must be selected from that group of compounds which fall within the generic formula:

wherein R is selected from the group consisting of hydrogen and --CH CH OH, and R is selected from the group consisting of H, CH CH OH, CH CH NH and alkyl radicals containing from 1 to 3 carbon atoms. As

used herein, ethanolamine compound includes ethanolamine and derivatives thereof as defined by the above formula.

Although applicant does not wish to be bound by theory, it is believed that the ethanolamine compound imparts a chelating action with respect to heavy metal ions present in the aqueous treating solutions. Such ions are obtained largely from alloying components present in the aluminum articles.

It is also believed that this essential constituent aids in brightening aluminum surfaces. Moreover, this essential component, because of its solvency action, aids in the removal of certain soils found on many aluminum articles being treated. In addition, the ethanolamine compound is essential in the formulations of this invention in providing physical stability to the concentrate.

With respect to the amount of ethanolamine compound present in the formulations of this invention it has been found that this material must be present in a quantity of not less than about 1.7% and should not exceed about 38% by weight of the total composition, depending upon the quantities of other materials present.

Where the amount of ethanolamine compound utilized is less than about 1.7 of the total composition, there may be insufficient chelation action for heavy metal ions thereby resulting in undesirable precipitation of metallic deposits on the surfaces of the aluminum articles being treated. Use of less than the minimum amount of ethanolamine compound will also result in failure to obtain desirably clean and bright aluminum surfaces. The amount of ethanolamine compound can be greater than about 38% by weight, but from an economic standpoint it is not desirable to use such larger amounts.

As to the exact concentration of ethanolamine compound required to yield a concentrated aqueous composition of this invention with all of the improved properties as heretofore described, it must be stated that for any given formulation of sodium and/ or potassium hydroxide, sodium and/or potassium gluconate, ethylenerglycol compound and water, there will exist such a concentration of ethanolamine compound below which the full formulation stability will not be realized. While such minimum amounts of ethanolamine compound will lie within the range of about 1.7% to about 38% by weight of the total formulation as heretofore specified, use of less than the minimum amount, which may still lie within the specified range, will result in the separation of the formulation into incompatible phases. That is to say, in certain formulations, those formulations containing relatively high amounts of potassium hydroxide, gluconate and ethyleneglycol compound in particular, the amounts of ethanolamine being on the lower side of the specified range may not result in a completely homogenous aqueous concentrate. For example, if 10 grams of an ethyleneglycol compound are added to a mixture of 60 grams of potassium hydroxide, 11.5 grams of potassium gluconate, 80.5 grams of water and 25 grams of triethanolamine, mixed thoroughly and examined, the result will be seen to be a non-homogenous mixture. Calculations show the following:

Example I Percent by weight Potassium hydroxide 32.0 Gluconate ion (as K salt) 6.15 Ethyleneglycolmonobutylether 5.34 Triethanolamine 13.37 Water 43.14

oughly dissolved to provide the composition of Example 11 below, the result is a true homogenous, stable, consolute, concentrated aqueous embodiment of the present invention.

Example II Percent by weight Potassium hydroxide 29.85

Gluconate ion (as K salt) 5.72 Ethyleneglycolmonobutylether 4.98 Triethanolamine 19.40 Water 40.05

The minimum amount of any ethanolamine compound required for complete formulation stability will depend primarily upon the relative amounts of the other active materials present in the formulations of this invention. Where the amounts are relatively high, the minimum concentration of the ethanolamine compound will be relatively high. Where the amounts of other atcive materials are relatively low, the minimum concentration of the ethanolamine compound will be lowered accordingly.

Therefore, it can be readily seen, that where a specific concentration of ethanonlamine compound in one formulation results in a stable composition, in another it may be insuflicient for complete stability while in a third it may be far in excess.

To summarize, the concentration of the ethanolamine compound must be at least about 1.7 parts by weight, and must not exceed about 38 parts by weight. Within this range, the minimum concentration of the ethanolamine compound must meet a further requirement, that of being present in an amount large enough to establish and maintain a consolute single phase solution. The minimum concentration of the ethanolamine compound which meets this requirement, is, Within the above range, relatively high when the concentrations of the other active ingredients, (those other than water) is high, and is relaitvely low within the above range when the concentration of the other active ingredients is low.

In accordance with the method aspect of the present invention, the concentrate is prepared by first mixing with Water the three active ingredients other than the ethanolamine compound, that is to say, the hydroxide, the gluconate, and the ethyleneglycol compound. Then ethanolamine compound is added, and the solution is observed during the addition thereof. Suflficient ethanolamine compound is added to convert the partially prepared solution from twophase into a single phaes, in the event that is not single phase before the addition of the ethanolamine compound. By adding the ethanolamine compound last, assurance is obtained that a sufficient amount is added to yield a stable product, and the point at which such amount has been added can readily be observed.

In the interest of obtaining optimum formulation stability it should be noted at this point, that although the gluconate ion and/or alkaline hydroxide may be added in the form of their sodium salts, it is suggested, where a consolute, aqueous, concentrate of maximum physical stability is desired, that this sodium ion be employed only in relatively small amounts. This is particularly true in those embodiments of the invention containing large amounts of the ethyleneglycol compound and/or small amount of water. Maximum stability of the formulations of this invention are obtained using potassium ions.

In order to illustrate the surprisingly stable formulations of this invention there are presented below a number of examples prepared in accordance with the teachings of this invention. For most of the examples, data is also presented to indicate the temperature range over which the solutions remain stable, consolute, and single phase. These examples are presented solely by way of illustration and are not intended in any way to be construed as a limitation of this invention except as defined in the appended claims.

6 Example III Percent by weight Potassium hydroxide 31.48

Gluconate ion (as K salt) 6.98 Ethyleneglycolmonobutylether 5.62 Triethanolamine 17.46 Water 38.46

Example IV Potassium hydroxide 4.64 Gluconate ion (as K salt) 0.15 Ethyleneglycolmonobutylether 54.17 Triethanolamine 21.67 Water 19.37 Stable 0 to F.

Example V Potassium hydroxide 19.40 Gluconate ion (as K salt) 0.97 Ethyleneglycolmonobutylether 1.94 Triethanolamine 28.22 Water 49.47 45 to 190 F.

Example VI Potassium hydroxide 8.57 Gluconate ion (as K salt) 17.15 Ethyleneglycolmonobutylether 0.43 Triethanolamine 9.60

Water 64.35 6 to 190 F.

Example VII Potassium hydroxide 14.70 Gluconate ion (as K salt) 2.93 (Ethyleneglycolmonobutylether 14.70 Triethanolamine 27.93

Water 39.64 Stable 51 to 190 F.

Example VIII Potassium hydroxide 29.98 Gluconate ion (as K salt) 4.98 Ethyleneglycolmonobutylether 5.72 Triethanolamine 19.40

Water 40.00 22 F.- 190 F.

Example IX Potassium hydroxide 35.96 Gluconate ion (as K salt) 5.96 Diethyleneglycolmonoethylether 3.34 N-methyl-diethanolamine 6.82

Water 48.02 0 F.144 F.

7 Example XIII Percent by Weight Potassium hydroxide 10.35 Gluconate ion (as K salt) 5.17 Diethyleneglycolmonobutylether 4.97 Diethanolamine 38.10

Water 41.41 F. 190 F.

Example XIV Potassium hydroxide 41.98 Gluconate ion (as K salt) 4.57 Ethyleneglycolmonomethylether 2.43 Diethanolamine 1.74

Water 49.28 0 F. 190 F.

Example XV Potassium hydroxide 18.55 Gluconate ion (as Na salt) 3.71 Triethylene glycol 9.09 Ethyleneglycolmonoethylether 3.80 N-methyl-diethanolamine 6.40 Water 58.45 0 F. 190 F.

Example XVI Potassium hydroxide 32.10 Gluconate ion (as K salt) 5.63 Ethyleneglycolmonobutylether 5.96

Triethanolamine 18.15 Surfactant (Triton DF12, an ethoxylated straight chain alcohol) 0.43 Water 37.73

I claim:

1. A stable, consolute, concentrated, aqueous chemical composition, for use, upon dilution, as a cleaner and etcher of aluminum surfaces, said composition consisting essentially of: from about 4.6 to about 42 parts by weight of a hydroxide selected from the class consisting of sodium and potassium hydroxide, from about 0.15 to about 30 parts by weight of gluconate, from about 19 to about 64 parts by weight of water, from about 0.43 to about 54 parts by weight of an ethyleneglycol compound of the type having the formula 8 wherein R is selected from the group consisting of hydrogen and CH CH OH and R is selected from the group consisting of hydrogen,

-CH CH NH and alkyl radicals containing from 1 to 3 carbon atoms, said ethanolamine compound being present in an amount comprising at least about 1.7 parts by Weight and suflicient, in relation to the amounts and proportions of other components, to establish and maintain a stable, consolute, single phase solution, but not more than about 38 parts by weight.

2. A method for preparing a stable consolute concentrated aqueous chemical composition for use, upon dilution, as a cleaner and etcher of aluminum surfaces, comprising: mixing together from about 4.6 to about 42 parts by weight of a hydroxide selected from the class consisting of sodium and potassium hydroxide, from about 0.15 to about 30 parts by weight of gluconate, from about 19 to about 64 parts by weight of water, from about 0.43 to about 54 parts by weight of an ethyleneglycol compound of the type having the formula R OCH CH OR wherein R is selected from the group consisting of hydrogen and alkyl-radicals containing from 1 to 4 carbon atoms and R is selected from the group consisting of hydrogen, the -CH CH OH radical and the CH -CH OCH CH OH radical, and adding to said mixture an ethanolamine compound of the type having the formula R3 HO-CH2-CHz-N wherein R is selected from the group consisting of hydrogen and CH CH OI-I and R is selected from the group consisting of hydrogen, -CH CH OH,

CH -CI-I -NH and alkyl radicals containing from 1 to 3 carbon atoms, in an amount comprising at least about 1.7 parts by weight, and not more than about 38 parts by weight, the addition of said ethanolamine compound being continued at least until said solution becomes single phase, and at least said minimum amount has been added.

References Cited UNITED STATES PATENTS MAYER WEINBLA'IT, Primary Examiner US. Cl. X.R. 

